When the animal-lover opened the back door she found her friend's dog inside and she went to give it a pat. She had been playing with the dog the day before and had no reason to suspect it could attack her.
"I opened the door and the dog was in there and it was fine," she told ABC's 7.30. "I rummaged around and gave him a pat on the head and he was just nice and sweet and that's when it jumped on to my face."
Flying out at her, the Staffordshire-pit bull cross locked its powerful jaws around the side of her face and began shaking her.
"It shook me like a rag doll," she said. "I fell back and I could feel all the holes in my face. I could feel my nose hanging off to one side. You can see through my cheek to my teeth. That's when I realised that my whole life was going to change."
Doctors gave her emergency surgery, but her injuries mean she was unable to lift her upper lip due to muscle damage.
She spent a week in hospital and needed plastic surgery on her horrendous wounds.
However, the damage wasn't just physical. She told the show about the devastating effect of the attack on her confidence and her career.
She was even targeted by sick online trolls over her scars.
"I loved being a model because I could make myself feel good in my own skin," she said. "I always got told I had an exotic look. I was quite a bubbly person as well. And I could really show that in my pictures."
It was this confidence which propelled her into a successful career in the competitive industry and helped her gain almost 24,000 followers on her Instagram page.
"I used to be quite confident and now I'm really insecure about how I look," she said.
Ms Mackintosh has also been documenting her recovery on social media as she tries to get her modelling career back on track.
"I don't see myself in the mirror anymore, I find it quite hard to get work as a model, now I'm working two jobs trying to make ends meet to cover all my costs and save up for future surgery.
"I just feel like this has become my life now."
After what happened to her, and seeing a spate of vicious dog maulings on small children in Australia in recent months, Ms Mackintosh wanted to see big changes to dog ownership laws - and "dangerous" breeds like the Staffordshire-cross which attacked her to be banned.
"I just want to bring awareness," she said.
"You might not think it can happen to you, but it can."
Liz Walker, chief executive of the Victorian RSPCA, told 7.30 banning breeds "doesn't work" and the only solution was better training.
